Framework of Indian Soil Classification
Among soil terminology used, soil classification is perhaps the least popular among common people in India due to missing linkage of its direct applicability to management. The existing classification (USDA Soil Taxonomy) is subject to interpretation to find some suitable management options. Soil classification is discussed under pedology and its linkage to edaphology is merely a customary. Soil is a non-renewable dynamic natural resource, which is subject to production of suitable land use type. The level of productivity is also dynamic and subject to variation, but ready to be enhanced through management. As such, classification scheme in case of soil cannot be static and may be directly linked to management options so that it must be easily acceptable not only to every branch of soil science, but also among common people and farming community for scientific exploitation. How is a soil formed, what set of factors was responsible to assign a well defined process in horizonation of a pedon and whether the soil body is pedogenic or merely disturbed are all related to what is called pedology. Soil as a resource is, however, more related to edaphology, wherein management approach is intended to its relation with plant nutrition and growth. The classification of a soil is thus ultimate expression that must be easily understandable in management terms to the common users and farmers. Lack of mutual relationship between pedology and edaphology during classifying a soil restricts the farmer’s acceptance for soil classification and, as a result, this limits its popularity merely within a class-room or in a scientific gathering.
Soils of Indo-Gangetic plains are often deep forming almost levelled plain with imprint of stratification under recent to youthful stage of pedogenesis (Fig 2)) particularly in case of tal and diara soils (Mishra et al. 1994, Mishra 2015b). They do differ in their structural orientation from platy to often prismatic via blocky structure. Under soil moisture stress from dryness to wetness in a sub-tropical climate, the length of growing period (LGP) may be considered relevant in classifying the soils. The Vertisols on basaltic hill top (summit) may often be identical to their counterpart in depression (foothill), though the LGP of hill top is much shorter as compared to depression. Stratification as affected by sand layer or even hardpan in a given profile may shrink the LGP. Both LGP and stratification seem to be integral in classification scheme.
Disturbed soils often remain partly attended in the classification schemes. Not only the soils of kitchen gardens or in flower’s pots, but most often, agricultural fields are also disturbed or transferred from other plots. The classification scheme must consider the disturbed materials, since they are essentially relevant to agricultural activities. Sand dunes, eroded and truncated materials and fluvial deposits are some other examples similar to disturbed soils, which reflect deviation from pedogenic definition of a soil (Mishra 2015b).
Accordingly, with the bare facts that soil is dynamic and works in an open system as affected by surrounding environment and susceptible to risks, hypothesis is developed that soil classification may not be stable and thus it may be developed in flexible mode. Fortunately, India has a vast database on established groups of soils besides benchmark soils as well as on land use planning projects from different sources. Within such strong background, it was conceived as a vision to develop Indian system of soil classification that must serve the bare need of the farming communities simply by linking the land suitability options so that the system would be demand driven. Accordingly, a framework was developed (Mishra 2013) as a mission in which existing information after due synthesis based on ground truthing would be tested following their validation. The ultimate goal is to integrate classification scheme (Soil group, Soil sub-group and Soil phase) with land suitability so that land use planning could be fixed.
Soil Classification structure
The highest category named “Soil Group” relates to the inherent soil qualities and altogether 17 Soil groups are assigned in the first hand approach (Table 3). Followed by this is the Soil sub-group which consists of six components relevant to the soil potentiality (Table 4). The soil sub-group will follow the Soil phase (consisting of five categories of constraints) that refers to the limitations associated with the actual productivity of a soil (Table 5). Both Soil sub-group and Soil phase during classification help in identifying the limitations associated with the soils so that improvement could be made possible by suitable management options (Land suitability).
Table 4. Soil sub-groups assigned to Soil groups
Sr. No. Soil sub-group (potentiality of a soil) Specific traits of the soil potential
1 Mode of profile arrangement Stratification
2 Effective depth of soil profile Shallow (< 25 cm)
Slightly deep (25-50 Cm)
Moderately deep (50-100 cm)
Deep (100-150 cm)
Very deep (>150 cm)
3 Length of growing period (LGP) Moist (>180 days)
Dry and moist (90-180 days)
Dry (<90 days)
4 Dominant clay minerals Kaolinite-Halloysite
5 Textural arrangement below 25 cm depth Sandy loam
6 Slope gradient Leveled (< 2%)
Table 5. Assignment of phases as the constraints against soil productivity.
Soil phase Characteristics associated with soil productivity Level
Soil fertility level Low organic matter, nutrient availability and their interaction state etc. I
Soil physical constraints Drainage, water storage capacity, temperature, gravels & stones etc. II
Soil chemical/mineralogical constraints Low CEC, high reduceable Fe2O3, high gypsum, salt, acidity, oxidic materials, quartz etc. III
Soil sickness/predators Microbial imbalance, termites, protozoa, nematodes, soil borne diseases etc. IV
Risks, uncertainties and doubts Flood, drought, erosion, climatic shift, CO2 & N2O emission etc. V
Table 6. Example to classify an Indian soil following scientific management
Soil group Sub-group Soil phase Most preferred land use choice (rotation)
Fluvisol Stratified, very deep, dry & moist, mixed, loam, gentle I, II, V Kalai (Phaseolus mungo)-Maize (Zea mays)-Cheena (Panicum millaccum)
As already reported (Mishra 2015c), the classification structure for a given soil may be written in sequence as Soil Group-Soil Subgroup- Soil Phase following the identification of associated limitations and subsequent correction through improvement measures in order to assign the most preferred land use choice in rotation (land suitability). In classification process, each soil group, for example, Fluvisol will include all six subgroups and associated phases in order to resolve the limitations for management option so that the land use planning may be specifically defined in the classification scheme itself (Table 6).
Soil Classification vs Corporatization at farmer’s door
Since the soil is basically a resource intended for management by the farmers, who care for business, there is logistic to shift this business towards insured profitability, because more than 75 percent of Indian population rests on this business. Therefore, the key factor for success in this giant business lies on the best agricultural practices followed by best business strategies. So, there must be the vision to empower the poor farmers with current reliable technological updating in order to compete with the emerging business environment and its processes, because the strength of any business depends on specific business process applied in line with excellence in production. Farmers are made aware to latest knowhow about business management process in order to enable them to adopt such process. In order to mobilize farmer’s mindset to incline to business tips, the first and foremost option is to familiarize them with success stories of identical farmers in the adjoining farming areas simply to sensitize for being committed for farming business management. Sushil Kumar, for example, in a village Tulsipur (Naugachia) of Bhagalpur district in Bihar (India) once brought some banana suckers and planted in his farm in the year 1971-72 with agronomic management inputs he learnt in Maharastra. The success story he planted was so reliably acceptable that other farmers not only in his village, but from adjoining villages started following this practice of banana cultivation. The adoption of banana cultivation was so revolutionary that within five years, entire Naugachia, Khagaria, Katihar and Purnea districts in India is known as “Kelanchal” i.e. Land of Banana. Importantly, the farmers never receive any encouragement in any way either through the state or central government, but the business zeal among the farming community of the zone left no stone untouched in order to make the profession profitable. Such examples, however, suffers from imbalanced business management process and thus the outcome may be profitable, but it cannot be stable and sustainable. So, the farmers are made well trained with business process under farming system. In the modern scenario, the business process works in networking, wherein production at one end follows the product being supplied through a well defined supply chain covering the priority area of demand. Thus, the land use based soil classification will promote the agricultural corporatization at the farmer’s door.
Soil classification vs Evergreen agriculture
The land use planning following the introduction of conservation agriculture (CA) by keeping the land covered with vegetation and/or crop residues round the year with least or zero tillage may serve the purpose of carbon sequestration as well as agricultural corporatization. The CA follows the principles of restoring the biodiversity and pedo-ecosystem. Selection of site-specific crop rotation based on parametric land evaluation followed by land use suitability identification may be the prerequisite for a given field plot. In this particular agriculture, one suitable cover crop is identified between two main crops based on nature and height of main crops already identified and such exercise needs exhaustive experience with indigenous knowledge and this may enable a soil scientist to work together with farmers in an interactive environment. Then, fix the balanced nutrition to the crops in rotation (including cover crops) based on soil fertility evaluation.
Soil covered with vegetation round the year may buffer the diurnal temperature change and minimize the organic matter decay considerably, thus, creating a congenial environment for C-sequestration. As farmers seek to change from chemical-based conventional farming systems to more sustainable kinds of agriculture i.e. organic farming, which may be adopted in conservation agriculture (CA) successfully, wherein one has to be sincere to use accessible organic sources like (i) crop residues comprising of both shoot and root residues (ii) plant debris in suitable sizes (< 2 mm but larger than 0.053 mm) (iii) humus (decomposed materials less than 0.053 mm that are dominated by molecules stuck to soil minerals) and (iv) compost, FYM, vermicompost and others, which are prepared locally (Bowden 2009). In CA, farmers should essentially learn, ahead of managing the organic resources, how to sustain soil moisture by managing organic source itself. The amount of plant available water can be determined by two parameters: (i) the lower limit i.e. the amount of water in the soil that plants cannot extract or utilize and (ii) the upper drained limit i.e. the amount of water that can be held against drainage. The difference between the upper and lower limit does define the potential available water holding capacity (PAWC) of a given soil. If this value can be increased even marginally through CA, it will help to sustain or simply maintain or optimize the potential productivity by allowing the soil to retain more water each time that rains. For any given clay content, as organic carbon increases the upper limit, the PAWC of the soil increases further (Bowden 2009). The amount of carbon in a soil results from the balance between inputs (plant residues or other sources) and losses (microbial decomposition and associated mineralization). Higa & Parr (1994), while advancing the concept of “Effective Microorganisms” (EM) rightly stated that the transition from conventional agriculture to organic farming can involve certain risks, such as initially lower yields following the increased pest problems. Once through the transition period, which might take a few years, farmers may find their new farming systems to be stable, productive, manageable and profitable without pesticides.
The soil C sequestration is truly a win–win strategy. It restores degraded soils, enhances biomass production, purifies surface and ground waters and reduces the rate of enrichment of atmospheric CO2 by offsetting emissions due to fossil fuel (Lal 2004a, 2004b). The sustainable production using conservation agriculture may be a win-win-win-win outcomes viz. good for soil, good for livestock, good for human nutrition, good for the environment and good for farmers, but importantly best for mitigation of climate change, although gradually to attain a steady rate, if organic resource is continually applied within the limit of SOM turnover. Thus, the proposed soil classification scheme in India may be popularized both for carbon sequestration, corporatization and road map of Indian agriculture in a big way.
The proposed 17 Soil groups are assigned to major soils of India at the highest level followed by Sub-groups (consisting of six potentially viable soil features for each Soil group) and Soil phase (consisting of five distinguishing constraints related to soil productivity). A classified soil may enable to identify the associated limitations for correction through the process of improvement measures in order to assign the most remunerative land use choice in rotation. The classification scheme is not only simple and acceptable, but an effective tool to integrate the conventional soil survey, land evaluation and land use planning with land suitability by merging the pedogenic aspects with edaphology. This further necessitates an opportunity to re-define a soil in management terms.
The intention as conceived from WRB was to work towards development of a framework through which ongoing national soil classification programme could be harmonized. Hence, there is need to reach an agreement on proposed levels of groupings for classifying the Indian soils through exchange of additional information as well as experience so that common scientific language could be developed to strengthen “A Model for Soil Classification System in India”.
The soil is highly dynamic in time and space in an open system and so its classification would also be changing in an interval that will vary according to surrounding and inherent conditions. As such, soil classification as an indicator of the land use planning would work directly for farming communities and justify as a tool to control food security, food safety and livelihood in a big way. The road map of the country based on soil classification would now help the policy makers to come up with reliable outcome through land use planning.
If the Government of India has any plan to launch a “Road Map of Agriculture in India”, the soil classification system as forwarded will be proved an asset to delineate the soils of India on land use options and related attributes desired for road map purposefully. The Classification scheme forwarded is simple, reliable, flexible and acceptable at farm level without imposing any complexity of nomenclature and diagnostic features. The researchers and students should verify its reliability in order to promote the effective utilization of land use planning in days to come.
Soil is the true foundation base to connect our life with food, air, water, climate, biodiversity and even energy for survival and nourishment. It is not only a huge reservoir of biodiversity, but also works for protective medical treatments. It is a source of construction and raw material as well as used in industry and nanotechnology even. Prime agriculture land without healthy soil is far off the truth and evidence. So, there is need to follow a work culture in soil science. Shrinkage of farm land either due to erosion or degradation or even non-farming activities like construction of houses or roads is the most terrifying consequence causing climate change and carbon emission. Evergreen or conservation agriculture is the most powerful mitigation option to combat with challenges of climate change. There is thus need to develop a strong global support in order to pay true respect to soil. The road map of agriculture without proper soil evaluation and land use suitability classification is virtually a missing gap, because ignorance of truth and reality results into disastrous consequences. The classification scheme for Indian soils will integrate soil qualities with soil health, associated limitations including climatic shift and land use suitability. In road map of the country, this system of soil classification will be a yardstick to ensure business oriented sustainable agriculture in India too.
* Contributed by Digital Green